JSFiddle - React, Tailwind, and code Playground

HTML

<label for="showblock">Show Block</label>
<input type="checkbox" id="showblock" />

<div id="block">
    Hello World
</div>

CSS

#block {
    background: yellow;
    height: 0;
    overflow: hidden;
    -webkit-transition: height 300ms linear;
    -moz-transition: height 300ms linear;
    -o-transition: height 300ms linear;
    transition: height 300ms linear;
}

label {
    cursor: pointer;
}

#showblock {
    display: none;
}

#showblock:checked + #block {
    height: 40px;
}